The Club for Growth backed a primary challenge to longtime Rep. Mike Simpson, R-Idaho, in its first major endorsement of the cycle.

On Wednesday, the influential conservative group announced its support for Bryan Smith, an attorney, to challenge Simpson, an eight-term member and close ally of Speaker John A. Boehner of Ohio.

"We met with Bryan months ago after hearing about him through PrimaryMyCongressman.com, and we’re confident that he’ll be a strong conservative alternative to RINO incumbent Mike Simpson," Club for Growth President Chris Chocola said in a press release.

"It’s time for Idaho voters to throw Mike Simpson out, and Bryan Smith is the man to replace him,” added Chocola, a former congressman from Indiana.

The club interviewed Smith in early May in Washington, D.C., and conducted a poll on his viability later in the month, according to a timeline provided in the release.

Smith raised $147,000 in his second fundraising quarter, according to a campaign release.

The club will continue to search for primary challengers to additional House Republicans listed on their PrimaryMyCongressman.com website. Their targets include National Republican Congressional Committee Chairman Greg Walden of Oregon, Reps. Adam Kinzinger and Aaron Schock of Illinois, Rep. Rick Crawford of Arkansas, Rep. Frank D. Lucas of Oklahoma, Rep. Steven M. Palazzo of Mississippi, Rep. Martha Roby of Alabama, Rep. Larry Bucshon of Indiana and Rep. Renee Ellmers of North Carolina.